MINOR LOSSES IN THE PIPE SYSTEM
Object: To determine the coefficient of resistance due to a socket shut-off gate valve.
Apparatus: fluid friction apparatus; hydraulic bench; socket shut-off gate valve; and stopwatch.
Fig. Fluid friction apparatus
Theory: The minor loss due to a 90o elbow is a function of velocity head and is written as
hl = K
ssgv
𝑣2
(1)
.
2𝑔
where
hl = loss of head due to Elbow
V = velocity of flow = Q/A
Kssgv = Coefficient of resistance due a socket shut-off gate valve
Area of flow = A = 𝜋 d2 = 3.14
(1.5)2 = 1.77 cm2
44
(since d = 15 mm = 1.5 cm)
Putting values in Eq.(1),
Kssgv = 2𝑔
𝑣2
Procedure:
. ℎ𝑙 =2 x 981
()
𝘘 2
1.77
. ℎ𝑙= 6147 . ℎ𝑙
𝑄2
(2)
- Fill the tank of the hydraulic bench with clean water.
- Connect the fluid friction apparatus with the hydraulic bench.
- Open the valve(s) that allow flow to the section under consideration and close all the irrelevant valves of the pipe friction apparatus.
- Connect the two ends of the tubes to the pressure-tapping nipples b/w the interchangeable section and the manometer.
- Slightly open the flow control valve at the hydraulic bench.
- Remove air bubbles from the tubes by opening the vent valve and drain valves of the differential manometer.
- Read the heads in the monometers corresponding to the pressure along entry and exit of the slanted seat valve.
- Collect water in the volumetric measuring section of the hydraulic bench. Read the volume collected as well as the time taken to collect that volume of water.
- Open the Flow control valve at the hydraulics bench slightly more for taking new reading.
- Repeat steps 7 and 8 to observe new readings.
- Carry out computations as per below table -1 and compare the range of Kssgv for a socket shut-off gate valve with that given in the literature, i.e. Kssgv 1-1.5
- In order to investigate the throttling behavior of socket shut-off gate valve, carry out the computations as per below table-2 and plot the graph b/w discharge and rate of opening valve.
Observations and Calculations:
Table-1
S. No. | Head (cm) | Discharge (cm3/sec) | Kssgv = 6147 . ℎ𝑙 𝑄2 | |||||
h1 | h2 | hl = h1 – h2 |
|
| T | Q = | ||
(cm) | (cm) | (cm) | (lit) | (cm3) | (sec) | (cm3/sec) | ||
1 | ||||||||
2 | ||||||||
3 | ||||||||
Average Kssgv = | ||||||||
Table-2
Socket Shut-off gate valve | ||||
Revolutions | Discharge in Cm3/sec | |||
|
| t | Q = | |
(lit) | (cm3) | (sec) | (cm3/sec) | |
0 (closed) | ||||
1/2 | ||||
3/4 | ||||
1 | ||||
1 ¼ | ||||
1 ½ | ||||
1 3/4 | ||||
2 | ||||
2 ½ | ||||
3 | ||||
3 1/2 (fully open) | ||||
Graph:
Comments:
